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Jan 22, 2017

EL-Wire Rope Dart

Made a glowing rope dart with EL-Wire! A rope dart is one of those spinning-arts props where there's a ball-weight on one end and a long trailing rope. Usually the ball is either glowing or on fire, so the light trail adds extra art to the performance.

A less common way to do it (the way I did it), was light up the rope itself. You still get interesting light trails, but the focal point is on the flow of the rope.

Zach being badass and testing out the new toy

Kris being badass and testing out the new toy

None of these photos are of me, by the way. I don't know how to spin things, but my friends are really cool and their hobbies prompt interesting presents. (Also Kris has a website)

Now construction:

EL wire has a phosphor layer that glows under AC current and really high voltage. Unlike LEDs, this mechanism produces a continuous strand of light and in general can handle tighter bends.

http://www.elwires.co.za/images/type_of_wire.jpg

Since EL wire is becoming increasingly popular in hobby applications (costumes, decoration, silly projects) you can easily find commercial inverters that convert DC power to the ~90V, 1000Hz AC power necessary to excite the phosphors. I just bought mine from Adafruit, connected the wires, and was good to go (minus having fun turning stuff on before soldering anything and subsequently managed to mildly-electrocute myself. High voltage doesn't mess around!)

Unfortunately, the physics of EL-wire force the inverters to resonate in audible frequency. So when this stuff is lit, there's an accompanying horrible high-pitch whine. In this project, the whine is made slightly better by stuffing the inverter into a box and into a pocket... but you can still hear it 10+ feet away.

Exceedingly minimal EE required

The electronics box was also really simple - inverter, switch, battery pack. It uses AA batteries so it can safely ignore recharging and be forgotten about, which I decided was worth sacrificing weight and form factor. The removable battery pack fits in the bottom half of a 3D-printed snap-fit box, and the inverter and on/off switch were hotglued into the top.

Got the snap-fit on the second try!

EL-wire isn't meant to take much load, so the structural rope consists of 1/4" non-chafing braided cotton line. The wire was woven through, and attaches to a connector on the box. The structural rope also feeds into a box and is constrained by a knot.

It ended up being surprisingly bright! The rope itself is also slightly heavier and has more friction than normal, but not too bad.